So I ended up returning the rental car with extra fuel. Despite my best efforts, I have vastly underestimated the fuel efficiency of the Toyota Camry and ended up with an extra 1/4 tank of fuel.

I ask the Alamo return guy about the possibility of a refund, and he is nice enough to take $10 off my final bill. Still made a net loss given the obscenely high price of fuel in CA.

Next time, I am not going to accept a rental car with less than a full tank of fuel.